1. Field of the Invention
The present invention relates to a film type compensation cell for an LCD(Liquid Crystal Display) and a method of manufacturing the same, and, more particularly, to a thin film type compensation cell for an LCD which has a compensation effect equal to that of a double STN (Super Twist Nematic) LCD and a method of manufacturing the same.
2. Description of the Prior Art
The light reflecting characteristic of the liquid crystal is changed in accordance with the voltage applied from the outside. And the LCD is a device for displaying characters, numbers, pictures and the like by using the dielectric characteristic of the liquid crystal.
A conventional LCD includes two parallel glass substrates between which spacers are inserted to maintain a constant gap between the glass substrates and the gap is filled with liquid crystal.
When an electric field is formed between opposing transparent electrodes disposed between the two glass substrates, the liquid crystal is twisted to a direction prescribed by an orientation layer disposed between the glass substrates by the dielectric anisotropy of the liquid crystal such that incident light from the outside is refracted by, or passed through the molecules of the liquid crystal arranged in the prescribed direction.
To colorize the LCD, the liquid crystal cell must be black and white. However, in a known STN LCD, when the twisted angle of the liquid crystal is 240 degrees, the light passing through a cell of liquid crystal is elliptically polarized so that the liquid crystal cell has the color of yellow, green, blue and the like.
A double STN LCD has been made to compensate for the color of this prior art STN LCD. In this double STN LCD, if a twisted angle of the liquid crystal molecules in a driving cell is +240 degrees, a compensation cell having a twisted angle of -240 degrees is piled up on the driving cell to compensate for the color of the driving cell.
In this double STN LCD, the driving cell has a common electrode and segment electrode, and the compensation cell has an orientation layer restricting the twisted angle of the liquid crystal only.
This double STN LCD is too thick. That is, the double STN LCD includes two liquid crystal cells each having two glass substrates that are expensive and thick.
To solve the above problems, a method for compensating for the color by using a compensation film having an optical anisotropy is known. In this method, a sheet of compensation film is piled up on the upper and lower sides of the driving cell of the LCD to compensate for the color of the STN LCD to the black/white. But, while this type of the LCD having the compensation films is thin enough, the compensation effects are not good enough.
Further, while the optical characteristic of the driving cell of the STN LCD changes when there is a temperature change, the optical characteristic of the compensation film does not change when there is a temperature change and it is difficult to effectively compensate for the color, and, therefore, the contrast of the LCD deteriorates as the temperature changes.